Aviation-grade kerosene from independently produced blendstocks

ABSTRACT

Aviation-grade kerosene comprising a first blendstock derived from non-petroleum feedstock and comprising primarily hydrocarbons selected from the group consisting of isoparaffins and normal paraffins, and a second blendstock comprising primarily hydrocarbons selected from the group consisting of cycloalkanes and aromatics.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application which claims the benefitunder 35 U.S.C. §121 of U.S. patent application Ser. No. 12/147,783,filed Jun. 27, 2008, which claims the benefit under 35 U.S.C. §119(e) ofU.S. Provisional Patent Application No. 60/947,126, filed Jun. 29, 2007,the disclosures of each of which are hereby incorporated herein byreference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under contractW911NF-07-C-0046 awarded by the Defense Advanced Research ProjectsAgency (DARPA). The government has certain rights in the invention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to aviation-grade high-cetanekerosene fuel. More particularly, herein disclosed is an aviation-gradekerosene fuel produced in part or fully from non-petroleum feedstocks.Specifically, the disclosed kerosene fuel comprises at least twoindependently produced blendstocks, with the first blendstock comprisingprimarily isoparaffins and normal paraffins (I/N) derived fromnon-petroleum feedstocks and the second blendstock comprising primarilycycloalkanes and aromatics (C/A) derived from petroleum or non-petroleumfeedstocks. In embodiments, a kerosene fuel suitable for use as aviationturbine fuel having drop-in and fit-for-purpose compatibility withconventional petroleum-derived fuels comprises up to 95 volume percent(vol. %) I/N blendstock and up to 35 vol. % C/A blendstock.

2. Background of the Invention

The generic term “kerosene” is used to describe the fraction of crudepetroleum that boils approximately in the range of 293° F. to 572° F.(145° C. to 300° C.) and consists of hydrocarbons primarily in the rangeof C₈-C₁₆. Kerosenes are the lighter end of a group of petroleumsubstances known as middle distillates.

As an example, the predominant use of high-cetane kerosene in the UnitedStates is aviation turbine fuel for civilian (Jet A or Jet A-1) andmilitary (JP-8 or JP-5) aircraft. Kerosene-based fuels differ from eachother in performance specifications. Jet A and Jet A-1 are kerosene-typefuels. The primary physical difference between Jet A and Jet A-1 isfreeze point (the temperature at which wax crystals disappear in alaboratory test). Jet A, which is mainly used in the United States, musthave a freeze point of −40° C. or below, while Jet A-1 must have afreeze point of −47° C. or below. Jet A does not normally contain astatic dissipater additive, while Jet A-1 often requires this additive.There are additional differences between the two fuels, and fullspecifications are outlined under the ASTM D1655 and Def Stan 91-91/5standards, respectively.

Military turbine fuel grades such as JP-5 and JP-8 are defined byMil-DTL-5624 and Mil-DTL-83133, respectively. These fuels arekerosene-type fuels made to more exacting specifications than thecommercial jet fuels. They also contain unique performance enhancingadditives. Throughout the world, many governments have issued a varietyof standards such as for TS-1 premium kerosene, TS-1 regular kerosene,and T-1 regular kerosene in Russia. The crude oil fraction for all ofthese aviation-grade kerosenes is basically limited to the range of 300°F. to 500° F. (149° C. to 260° C.), with additional specifications basedon recovery rates at given temperature points. Hydrocarbons areprimarily in the range of C₈-C₁₆.

The ready availability of crude petroleum has encouraged theestablishment of the above-mentioned specifications for kerosene as thebasis for fuels in engines of various types, and engines have thus beenoptimized to run on kerosene having these specifications. Concern hasarisen regarding the reliability and availability of the petroleumsupply. This concern has stimulated a search for substitutes. Liquidsderived from coal, shale, tar sands, and renewable resources such asbiomass, in particular, plant material, have been proposed. Theseprocesses have not adequately produced aviation-grade kerosene thatcomplies with today's jet fuel specifications.

The failure of obtaining suitable aviation-grade kerosenes fromnon-petroleum feedstocks has triggered development in downstreamprocessing of the products. For example, U.S. Pat. No. 4,645,585discloses the production of novel fuel blends from hydroprocessinghighly aromatic heavy oils such as those derived from coal pyrolysis andcoal hydrogenation.

International Patent WO 2005/001002 A2 relates to a distillate fuelcomprising a stable, low-sulfur, highly paraffinic, moderatelyunsaturated distillate fuel blendstock. The highly paraffinic,moderately unsaturated distillate fuel blendstock is prepared from aFischer-Tropsch-derived product that is hydroprocessed under conditionsduring which a moderate amount of unsaturates are formed or retained toimprove stability of the product.

Although many physical properties for aviation-grade kerosene can bematched and even outperformed, the fuels derived by hydroprocessing andadditional upgrading as described above do not provide drop-incompatibility with conventional petroleum-derived aviation-gradekerosene, as they lack some of the major hydrocarbon constituents oftypical petroleum-derived kerosene.

An attempt for better modeling of the variety of different hydrocarbonconstituents was made by Violi et al. (Violi, A.; Yan, S.; Eddings, E.G.; Sarofim, A. F.; Granata, S.; Faravelli, T.; Ranzi, E.; Combust. Sci.Technol. 2002, 174 (11-12) 399-417). Violi et al. modeled JP-8 as asix-compound blend of well-known hydrocarbons with the following molarcomposition: 10% iso-octane (C₈H₁₈), 20% methylcyclohexane (C₇H₁₄), 15%m-xylene (C₈H₁₀), 30% normal-dodecane (C₁₂H₂₆), 5% tetralin (C₁₀H₁₂),and 20% tetradecane (C₁₄H₃₀). This surrogate blend simulates thevolatility and smoke point of a practical JP-8 fuel. However, thismethod of reducing the fuel to a mere six-compound blend does notreproduce all required performance specifications of JP-8.

A different route was pursued in U.S. Patent Application 2006/0138025,which relates to distillate fuels or distillate fuel blendstockscomprising a blend of a Fischer-Tropsch-derived product and apetroleum-derived product that is then hydrocracked under conditions topreserve aromatics. While this may produce some required characteristicsfrom certain petroleum feedstocks, such as seal swell and density, thisapproach reduces the ability to achieve competing characteristics, suchas freeze point specifications.

Accordingly, there is an ongoing need for a fuel and process that allowuse of environmentally-sensitive processes as a bridge to the future andprovide drop-in compatibility with existing petroleum-basedaviation-grade kerosene for clean fuels produced from secure domesticresources.

SUMMARY

Herein disclosed is aviation-grade kerosene comprising: a firstblendstock derived from non-petroleum feedstock and comprising primarilyhydrocarbons selected from the group consisting of isoparaffins andnormal paraffins, and a second blendstock comprising primarilyhydrocarbons selected from the group consisting of cycloalkanes andaromatics. In embodiments, the second blendstock is derived fromfeedstock comprising non-petroleum feedstock. It is desirable for theaviation-grade kerosene is capable of being blended withpetroleum-derived jet fuel in any proportion such that the resultingblend meets fuel grade specification of the petroleum-derived jet fuel.In embodiments, the aviation-grade kerosene comprises up to 95 vol. % offirst blendstock and up to 35 vol. % of second blendstock.

In specific embodiments, the aviation-grade kerosene comprises up to 95vol. % first blendstock, from about 0 vol. % to about 30 vol. %cycloalkanes, and from about 0 vol. % to about 15 vol. % aromatics. Inembodiments, this kerosene comprising up to 95 vol. % first blendstock,from about 0 vol. % to about 30 vol. % cycloalkanes, and from about 0vol. % to about 15 vol. % aromatics meets fit-for-purpose requirements.In embodiments, at least 50 weight percent of the kerosene is derivedfrom coal, natural gas, or a combination thereof. In embodiments, thesecond blendstock is derived from coal, biomass, oil-shale, tar, oilsands, or a combination thereof. In embodiments, at least 50 weightpercent of the kerosene is derived from biomass. In embodiments, atleast 10 weight percent of the kerosene is derived from non-crackedbio-oil.

Also disclosed herein is a method for the production of aviation-gradekerosene comprising: producing a first blendstock from at least onenon-petroleum feedstock, the first blendstock comprising primarilyhydrocarbons selected from the group consisting of isoparaffins andnormal paraffins; producing a second blendstock comprising primarilyhydrocarbons selected from the group consisting of cycloalkanes andaromatics; and blending at least a portion of the first blendstock withat least a portion of the second blendstock to produce aviation-gradekerosene. In embodiments of the method for the production ofaviation-grade kerosene, first and second blendstocks areindependently-produced. In embodiments of the method, the non-petroleumfeedstock is selected from the group consisting of coal, natural gas,biomass, vegetable oils, biomass pyrolysis bio-oils,biologically-derived oils and combinations thereof.

In some embodiments of the method, at least a portion of firstblendstock is produced via indirect liquefaction. Indirect liquefactionmay comprise Fischer-Tropsch processing of a feedstock selected from thegroup consisting of natural gas, coal, biomass, and combinationsthereof. The kerosene may comprise up to about 90 vol. % firstblendstock produced via indirect liquefaction.

In embodiments of the method for the production of aviation-gradekerosene, the at least one non-petroleum feedstock comprisestriglyceride and/or fatty acid feedstock. The kerosene may comprise fromabout 65 vol. % to about 75 vol. % of first blendstock, the at least onenon-petroleum feedstock for which comprises triglyceride and/or fattyacid feedstock. In embodiments, second blendstock is produced bycatalytic cyclization and/or reforming of a portion of first blendstock,the at least one non-petroleum feedstock for which comprisestriglyceride and/or fatty acid feedstock. The kerosene may compriseabout 65 vol. % first blendstock, the at least one non-petroleumfeedstock for which comprises triglyceride and/or fatty acid feedstock;and about 35 vol. % second blendstock produced by catalytic cyclizationand/or reforming of a portion of first blendstock.

In some embodiments, the kerosene comprises about 70 vol. % firstblendstock produced via catalytic processing of triglyceride and/orfatty acid feedstock and about 30 vol. % second blendstock produced viapyrolysis processing of high cycloalkane-content material.

In embodiments of the method for the production of aviation-gradekerosene, second blendstock is produced via pyrolysis of a feedstockselected from the group consisting of coal, oil shale, oil sands, tar,biomass, and combinations thereof. In specific embodiments, the kerosenemay comprise about 80 vol. % first blendstock produced viaFischer-Tropsch processing of natural gas, coal, and/or biomass andabout 20 vol. % second blendstock produced via pyrolysis processing ofcoal tar fraction.

In some embodiments of the method for the production of aviation-gradekerosene, the second blendstock is produced via direct liquefaction. Inembodiments, the kerosene comprises about 25 vol. % second blendstockproduced via direct liquefaction. In specific embodiments, the kerosenefurther comprises about 75 vol. % first blendstock derived fromFischer-Tropsch processing of natural gas, coal, and/or biomass.

In some embodiments of the method for the production of aviation-gradekerosene, second blendstock is produced from a biomass-derived ligninfeedstock. The kerosene may comprise from about 25 vol. % to about 30vol. % second blendstock produced from a biomass-derived ligninfeedstock. In some embodiments, the kerosene comprises about 30 vol. %second blendstock produced via pyrolysis processing of biomass-derivedlignin and about 70 vol. % first blendstock produced via Fischer-Tropschprocessing of natural gas, coal, and/or biomass. In embodiments, thekerosene comprises about 25 vol. % second blendstock produced from abiomass-derived lignin feedstock and about 75 vol. % first blendstockderived from catalytic processing of triglyceride feedstock.

In embodiments of the method for the production of aviation-gradekerosene, the method further comprises testing the aviation gradekerosene for at least one requirement selected from the group consistingof fit-for-purpose requirements, ASTM requirements, and combinationsthereof. In embodiments, the method further comprises adjusting theratio of first blendstock and second blendstock in the kerosene to meetat least one requirement selected from the group consisting offit-for-purpose requirements, ASTM requirements, and combinationsthereof. In some embodiments, the method further comprises adjusting theamount of cycloalkanes and aromatics in the second blendstock to meet atleast one requirement selected from the group consisting offit-for-purpose requirements, ASTM requirements, and combinationsthereof.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more detailed description of the preferred embodiment of thepresent invention, reference will now be made to the accompanyingdrawings, wherein:

FIG. 1 is a schematic of an indirect liquefaction process suitable forproducing isoparaffin/n-paraffin (I/N) blendstock according to anembodiment of the present disclosure.

FIG. 2 is a schematic of a pyrolysis process suitable for producingcycloalkane/aromatic (C/A) blendstock according to an embodiment of thepresent disclosure.

FIG. 3 is a schematic of a direct liquefaction process suitable forproducing cycloalkane/aromatic (C/A) blendstock according to anembodiment of the present disclosure.

FIG. 4 is a comparison of gas chromatography data from FT (FT derivedliquid fuel from natural gas—bottom) and Fuel Sample A (top) producedfrom two discrete blendstocks and technological processes: (1) anisoparaffinic kerosene (IPK) produced from FT technology and natural gasfeedstock and (2) an aromatic/cycloparaffinic blendstock produced frompetroleum feedstock.

FIG. 5 is a comparison of gas chromatography data from typical JP-8(bottom) and Fuel Sample C (top) produced from two discrete blendstocksand technological processes: (1) an isoparaffinic kerosene (IPK)produced from a crop oil feedstock and (2) an aromatic/cycloparaffinicblendstock produced from a crop oil feedstock.

NOTATION AND NOMENCLATURE

The term “I/N blendstock” as used herein refers to a material thatcomprises at least 95 weight percent of isoparaffins, normal paraffins,or a mixture thereof.

The term “C/A blendstock” as used herein refers to a material thatcomprises at least 95 weight percent of cycloalkanes, aromatics, or amixture thereof.

The terms “aviation-grade kerosene” or “jet fuel” as used herein referto kerosene-type fuels that are specified by military turbine fuelgrades such as JP-5 and JP-8 and defined by Mil-DTL-5624 andMil-DTL-83133, respectively, or civilian aviation jet fuels such as JetA or Jet A-1 with full specifications outlined under the ASTM D1655 andDef Stan 91-91/5 standards, respectively. Throughout the world thereexist a variety of similar standards that might change over time and areconsidered under this definition.

The term “fit-for-purpose requirements” as used herein refers to fuelproperty requirements that are not necessarily addressed by military orASTM standards, but are still important to fuel performance andstability in jet engines and during fuel handling, distribution, andstorage. Examples of fit-for-purpose requirements include fuelcompatibility with aircraft fuel and engine system materials ofconstruction, adequate fuel performance in compression ignition (versusturbine) engines in a wide variety of ground environments, and possiblefuel performance requirements related to swelling of elastomeric sealsin, for example, turbine engines.

The term “drop-in compatibility” as used herein refers to aviation-gradekerosene capable of being blended with petroleum-derived jet fuel in anyproportion (i.e. from 0% to 100%) such that the resulting blend meetsfuel grade specification and fit-for-purpose requirements of theequivalent petroleum-based jet fuel.

The term “I/N-C/A fuel” as used herein refers to aviation-grade kerosenederived from at least two independently produced blendstocks, with afirst I/N blendstock derived from non-petroleum feedstocks and a secondC/A blendstock derived from petroleum or non-petroleum feedstocks.

DETAILED DESCRIPTION I. Overview

Herein disclosed are a fuel and a method for making the fuel whereby thefuel has drop-in compatibility with existing petroleum-derived fuels andenables production of most or all of a fuel from domestic,non-petroleum, and/or renewable feedstocks. The method of making thisaviation-grade jet fuel may allow broad flexibility in fuel formulationin order to meet specific end-use requirements. The disclosed I/N-C/Afuel comprises a blend of fuel components, namely straight-chain(normal) and branched (iso-) paraffins, cycloalkanes, and/or aromatics.

Meeting a specification for aviation-grade kerosene requires providing acomplex mixture of fuel chemical classes that have conflicting effectson physical properties. For example, longer carbon chain molecules serveto reduce volatility and increase density, which in turn raises freezepoint above acceptable levels for high altitude flight. Balancing thesecharacteristics along with energy density, flash point, viscosity, smokepoint, seal-swelling capacity, and other characteristics makes fuelformulation difficult when derived from a single non-petroleum resource.

The aviation-grade kerosene herein disclosed is produced from at leasttwo independently-produced blendstocks, with a first blendstockcomprising primarily hydrocarbons selected from the group consisting ofisoparaffins and normal paraffins (I/N) and derived from non-petroleumfeedstocks and a second blendstock comprising primarily hydrocarbonsselected from the group consisting of cycloalkanes and aromatics (C/A)and derived from petroleum or non-petroleum feedstocks. In embodiments,the finished I/N-C/A jet fuel comprises up to 95 volume percent (vol. %)I/N blendstock and up to 35 (vol. %) C/A blendstock.

II. Kerosene

Petroleum-based kerosene may be obtained either from the atmosphericdistillation of crude oil (“straight-run” kerosene) or from cracking ofheavier petroleum streams (“cracked” kerosene). The kerosene is furthertreated by a variety of processes to remove or reduce the level ofundesirable components, e.g., aromatic hydrocarbons, sulfur, nitrogen,or olefinic materials. This additional processing also reducescompositional variation and enriches components that improve performance(cycloalkanes and isoparaffins, for example). In practice, the majorprocesses used are hydrodesulfurization (treatment with hydrogen toremove sulfur components), washing with caustic soda solution (to removesulfur components), and hydrogenation (to remove, for example, olefins,sulfur, metals, and/or nitrogen components). Aromatics that may haveformed during the cracking process are removed via solvent extraction.For instance, hydrodesulfurized kerosene is obtained by treating akerosene-range petroleum stock with hydrogen to convert organic sulfurto hydrogen sulfide, which is then removed. These subsequent treatmentsmay blur the distinction between straight-run and cracked kerosenes.

While kerosenes are essentially similar in composition, the precisecomposition of a specific kerosene-range refinery stream depends on thecrude oil from which the kerosene was derived and on the refineryprocesses used for its production. Because they are complex hydrocarbonmixtures, materials in this category are typically not defined bydetailed compositional data but instead by process history, physicalproperties, and product-use ASTM and similar specifications.

Consequently, detailed compositional information for the streams in thiscategory is limited. General compositional information on representativekerosene-range refinery streams and fuels, presented in Table 1,illustrates the fact that the materials in this category are similar inphysical properties and composition. Regardless of crude oil source orprocessing history, major components of kerosenes comprise branched andstraight-chain paraffins (iso- and normal or n-alkanes) and naphthenes(cycloparaffins or cycloalkanes), which normally account for at least 75vol. % of a finished fuel. Aromatic hydrocarbons in this boiling range,such as alkylbenzenes (single ring) and alkylnaphthalenes (double ring)do not normally exceed 25 vol. % of a kerosene product. Olefins areusually not present at more than 5% by volume. The distillation range ofkerosenes is such that benzene (80° C. boiling point) and normal-hexane(69° C. boiling point) concentrations are generally less than 0.01% bymass. The boiling points of the 3-7 fused-ring polycyclic aromaticcompounds (PACs) are well above the boiling range of straight-runkerosene streams. Consequently, the concentrations of PACs found inkerosenes are very low, if not below the limits of detection of theavailable analytical methods. A detailed analysis of a hydrodesulfurizedkerosene illustrates this and is presented as Table 2.

TABLE 1 General Kerosene Compositional Information HydrodesulfurizedKerosene Jet A JP-8 API Gravity   39-45.5 37.2-46.1 37.0-46.7 AromaticContent, vol. %   18-21.4 11.6-24.0 13.6-22.1 Olefin Content, vol. % 1.0-1.66 0.0-4.1 0.6-3.0 Saturates Content, vol. % 77.2-82   71.9-88.474.9-85.8 10% Distillation, ° F. 329-406 294-394 333-390 FBPDistillation, ° F. 451-568 404-510 419-474 (Final Boiling Pt.) (90%)(90%)

TABLE 2 Hydrodesulfurized Kerosene Component Weight Percent Nonaromatics80.27 Saturates 78.61 Olefins 1.66 Aromatics 19.72 Less than Three-RingPAC 19.72 Three- to Seven-Ring PAC <0.01

III. I/N Blendstock

The herein disclosed I/N-C/A blend fuel comprises at least one I/Nblendstock comprising primarily hydrocarbons selected from the groupconsisting of isoparaffins and normal paraffins, the hydrocarbonsderived from non-petroleum feedstock. The finished I/N-C/A jet fuelcomprises up to 95 vol. % of I/N blendstock. In embodiments, I/Nblendstock comprises isoparaffin and/or normal paraffin compoundscontaining primarily from eight to sixteen carbon atoms per molecule (C8to C16 compounds). In embodiments, these compounds are produced directlyvia a chemical process such as, but not limited to, Fischer-Tropschcondensation of synthesis gas (‘syngas’), thermocatalytic processing ofvegetable oils, pyrolysis, liquefaction, and gas-to-liquids processing.

In embodiments, I/N blendstock is derived from one or a combination ofthe following feedstocks: natural gas, coal, biomass, vegetable oils,biomass pyrolysis bio-oils, and other biologically-derived oils. I/Nblendstock can be produced by several routes. In a specific embodiment,as shown in FIG. 1, indirect liquefaction is used to produce I/Nblendstock. Indirect liquefaction feedstock, such as coal or biomass, 10is gasified in gasifier 40 with steam 20 and/or oil 30. Gasifiereffluent 50, may comprise carbon monoxide, hydrogen, carbon dioxide,hydrogen sulfide, and/or ammonia. Gasifier effluent 50 is purified andupgraded in step 60, whereby a contaminant stream(s) 70 comprising, forexample, hydrogen sulfide, ammonia, and/or carbon dioxide is removed.Syngas stream 80, comprising primarily CO and H₂, undergoes liquefaction90 to yield liquid products 100. In embodiments, liquid products 100 aresynthesized from syngas 80 by catalytic Fischer-Tropsch (F-T)processing. The Fischer-Tropsch reactions produce a wide spectrum ofoxygenated compounds, in particular, alcohols and paraffins ranging incarbon numbers from C₁-C₃ (gases) to C₃₅₊ (solid waxes). TheseFischer-Tropsch products yield distillate fuels that comprise C₈-C₁₆paraffins and, through isomerization, C₈-C₁₆ isoparaffins that haveexcellent cetane numbers and very low sulfur and aromatic content. Theseproperties make F-T products suitable for use as I/N blendstock.However, because of the lack of adequate cycloalkanes and aromatics,Fischer-Tropsch distillate fuels are typically unable to meet allmilitary and ASTM specifications and fit-for-purpose requirements.Therefore, as described further hereinbelow, I/N blendstock is blendedwith C/A blendstock to obtain aviation-grade I/N-C/A fuel. Inembodiments, I/N-C/A fuel comprises up to 95 vol. % I/N blendstock,alternatively about 90 vol. % I/N blendstock derived fromFischer-Tropsch processing of natural gas, coal, and/or biomass. Inembodiments, the I/N-C/A fuel comprises about 80 vol. % I/N blendstockderived from Fischer-Tropsch processing of natural gas, coal, and/orbiomass. In alternative embodiments, I/N-C/A fuel comprises about 70vol. % I/N blendstock derived from Fischer-Tropsch processing of naturalgas, coal, and/or biomass.

In embodiments, I/N blendstock is produced from triglyceride and/orfatty acid feedstocks. I/N blendstock n-paraffins may be produced, forexample, via: (1) catalytic triglyceride dissociation into fatty acidsand glycerol, (2) glycerol removal, and (3) oxygen removal from fattyacids (e.g., via catalytic decarboxylation and/or reduction) to yieldnormal paraffins. I/N blendstock isoparaffins may be produced via (4)catalytic isomerization of a portion of these normal paraffins to yieldisoparaffins.

In embodiments, I/N-C/A fuel comprises from about 65 vol. % to about 95vol. % I/N blendstock derived from catalytic processing of triglyceridefeedstock. In specific embodiments, I/N-C/A fuel comprises about 75 vol.% I/N blendstock derived from catalytic processing of triglyceridefeedstock. In alternative embodiments, I/N-C/A fuel comprises about 80vol. % I/N blendstock derived from catalytic processing of triglyceridefeedstock. In alternative embodiments, I/N-C/A fuel comprises about 80to 90 vol. % I/N blendstock derived from catalytic processing oftriglyceride feedstock.

IV. C/A Blendstock

As mentioned hereinabove, I/N blendstock typically has a density belowminimum requirements. For example, the I/N blendstock typically has adensity below the MIL-DTL-83133-specified minimum requirement of 0.775kg/L and may be very near to exceeding or may exceed the freeze pointmaximum requirement of less than −47° C. As it is desirable for theI/N-C/A fuel to meet standard (for example, MIL-DTL-83133-specified)density, freeze point, and flash point requirements, the disclosedI/N-C/A fuel further comprises at least one independently-produced C/Ablendstock to obtain required density and cold-flow performance. The C/Ablendstock comprises primarily hydrocarbons selected from the groupconsisting of cycloalkanes and aromatics. The aviation-grade I/N-C/Afuel comprises an appropriate blend of aromatics and cycloalkaneswhereby requisite density and freeze point specifications of theresulting high cetane kerosene fuel are met. In embodiments, thehydrocarbons of the C/A blendstock are derived from petroleumfeedstocks. In embodiments, the hydrocarbons of the C/A blendstock arederived from non-petroleum feedstocks. In embodiments, the hydrocarbonsof the C/A blendstock are derived from a combination of petroleum andnon-petroleum feedstocks. In embodiments, the I/N-C/A fuel comprises upto 35 vol. % C/A blendstock.

In embodiments, the C/A blendstock comprises aromatics. In embodiments,the C/A blendstock comprises aromatics selected primarily from the groupconsisting of C9 to C15 aromatics which provide the requisite density.In embodiments, the aromatics are primarily alkylated benzene compounds.In addition to providing density, aromatics may also contribute tobeneficial seal swelling and may provide needed lubricity and viscosity.In embodiments, the C/A blendstock comprises less than about 15 vol. %aromatics. In embodiments, the C/A blendstock comprises from about 0vol. % to about 15 vol. % aromatics.

In embodiments, C/A blendstock comprises cycloalkanes. In embodiments,the C/A blendstock comprises cycloalkanes primarily selected from thegroup consisting of C₉ to C₁₅ cycloalkanes which reduce freeze point (tocounteract the freeze point increase resulting from aromatic addition)without adversely decreasing flash point. In embodiments, C/A blendstockcomprises less than about 30 vol. % cycloalkane. In embodiments,suitable freezepoint are obtained in the I/N-C/A fuel by selection ofaromatics (i.e. having high density and low freezepoint) for the C/Ablendstock such that the C/A blendstock comprises 0% cycloalkanes. Inembodiments, C/A blendstock comprises from about 0 vol. % to about 30vol. % cycloalkane. In embodiments, jet-fuel compliant I/N-C/A fuelcomprises up to 95 vol. % of paraffins selected from isoparaffins andnormal paraffins, from about 0 vol. % to about 30 vol. % cycloalkanes,and from about 0 vol. % to about 15 vol. % aromatics. In embodiments,I/N-C/A fuel comprises about 95 vol. % I/N blendstock and about 5% highdensity low freezepoint aromatic.

Without limitation, C/A blendstock may be derived from one or acombination of the following feedstocks: petroleum, oil shale, oilsands, natural gas, coal, biomass, vegetable oil, biomass pyrolysisbio-oil, and other biologically-derived oils. In embodiments,aviation-grade I/N-C/A kerosene comprises at least 50 weight percent ofhydrocarbons selected from cycloalkanes and aromatics, said hydrocarbonsderived from coal, biomass, or a combination thereof.

C/A blendstock may be produced by several methods. FIG. 2 shows anembodiment for the production of C/A blendstock via pyrolysis (heatingin a deficiency of oxygen). Pyrolysis may be performed by any methodknown to one of skill in the art. In FIG. 2, pyrolysis feedstock 110undergoes pyrolysis 120. Suitable pyrolysis feedstock 110 includes,without limitation, coal, oil shale, oil sands, biomass, andcombinations thereof. Gases 140 and char/ash/minerals 130 are removed.Pyrolysis oil vapors are condensed, the resulting pyrolysis oil 150 ishydrotreated as is known to those of skill in the art. In embodiments,catalytic hydrotreating is used to reduce the level of at least onecontaminant selected from the group consisting of nitrogen, sulfur,oxygen, and metals. In embodiments, pyrolysis oil 150 is treated withhydrogen 180 and the level of sulfur and/or nitrogen in pyrolysis oil150 is reduced via elimination of gas stream(s) 170 comprising, forexample, hydrogen sulfide and/or ammonia. Via hydrotreating 160,contaminant-reduced liquid products 190 are obtained. This procedure issimilar to the procedure used in upgrading crude oil in a refinery toproduce a variety of liquid fuels, as known to those of skill in theart. Table 3 presents a comparison of pyrolyzed coal tar fractions basedon typical boiling range and major hydrocarbon constituents.

TABLE 3 Typical Coal Tar Fractions Boiling Typical HC ConstituentsFraction Range, ° C. and Carbon Numbers Ammoniacal Liquor ~100 — LightOil <170 Benzene, C₆; Toluene, C₇; Xylene, C₈ Middle Oil or Carbolic Oil170-230 Naphthalene, C₁₀ Heavy Oil or Creosote Oil 230-270 Naphthalene,C₁₀ Green Oil or Anthracene Oil 270-360 Anthracene, C₁₄ Residue orPitch >360 —

In particular, low-temperature tar and light oils formed fromsub-bituminous and bituminous coals at temperatures below about 700° C.as relatively fluid, dark brown oils that comprise phenols, pyridines,paraffins, and/or olefins. The oils are heterogeneous, with any onecomponent constituting only a fraction of a percent of the total mass.The lignite tars may also contain up to 10% of paraffin waxes, so theproduct has a “butter-like consistency” and solidifies at temperaturesas high as 6° C. to 8° C. The primary high-temperature tar vapors formedabove 700° C. are more homogeneous. The light oils are predominantlybenzene, toluene, and xylenes (BTX) and the tars are bitumen-likeviscous mixtures that contain high proportions of polycondensedaromatics. For the most part, the pyrolysis tars and oils are notsuitable final fuel products. Often they are unstable, and when warmed,they polymerize and become more viscous. Ash and mineral matter 130 isremoved in pyrolysis 120, which increases the heating value, but sulfurand nitrogen are not completely removed in pyrolysis 120. A more stableand useful product is obtained by hydrogenating 160 and removing thesulfur and/or nitrogen from the fuel as hydrogen sulfide and/or ammoniain stream(s) 170. These procedures are, as noted previously, similar tothe various refinery procedures used to upgrade natural crude oils. Thehydrotreated liquid products 190 may be further refined and upgraded, byany methods known to one of skill in the art, to yield a mix ofcycloalkanes and aromatics of which the C/A blendstock is comprised.

In embodiments, the I/N-C/A fuel comprises about 20 vol. % C/Ablendstock derived from pyrolysis processing of a coal tar fraction. Inembodiments, the I/N-C/A fuel comprises about 80 vol. % I/N blendstockderived from Fischer-Tropsch processing of natural gas, coal, and/orbiomass, and about 20 vol. % C/A blendstock derived from pyrolysisprocessing of coal tar fraction. In embodiments, I/N-C/A fuel comprisesabout 30 vol. % C/A blendstock derived from pyrolysis processing of ahigh cycloparaffin-content material derived from oil shale or oil sandfeedstock. In embodiments, I/N-C/A fuel comprises about 70 vol. % I/Nblendstock derived from catalytic processing of triglyceride feedstockand about 30 vol. % C/A blendstock derived from pyrolysis processing ofa high cycloparaffin-content material derived from an oil shale or oilsand feedstock.

In another embodiment of the invention, shown in FIG. 3, directliquefaction 220 of liquefaction feedstock 210 is used to produce C/Ablendstock. Liquefaction feedstock 210 may comprise, for example, coaland/or biomass. There are two basic procedures: hydroliquefaction andsolvent extraction. In hydroliquefaction, coal 210 is mixed withrecycled coal oil 230 and, together with hydrogen 240, fed tohigh-pressure catalytic reactor 220 where hydrogenation of coal 210takes place. In solvent extraction, also termed “solvent refining,” coal210 and hydrogen 240 are dissolved at high pressure in a recycledcoal-derived solvent 230 which transfers hydrogen 240 to coal 210. Afterphase separation 260, wherein gases 270 and ash 280 may be removed fromcoal liquid 250 which may be further cleaned and upgraded by refineryprocedures, liquid fuels 290 are produced. In solvent refining, with alow level of hydrogen transfer, a solid, relatively clean fuel termed“solvent refined coal” 290 is obtained. As in pyrolysis, the compoundsare similar to the coal tars and highly aromatic in nature.Hydrogenation and selective catalytic processing, as known to one ofskill in the art, may be performed to yield a mix of cycloalkanes andaromatics that provide the C/A blendstock.

In embodiments, the I/N-C/A fuel comprises about 20 vol. % C/Ablendstock derived from direct liquefaction of a coal feedstock. Inembodiments, the I/N-C/A fuel comprises about 80 vol. % I/N blendstockderived from Fischer-Tropsch processing of natural gas, coal, and/orbiomass, and about 20 vol. % C/A blendstock derived from directliquefaction of a coal feedstock.

In an embodiment, C/A blendstock comprises cycloalkanes obtained byseparation (e.g., via distillation or extraction) of cycloalkanesselected from the group consisting of C9-C15 cycloalkanes from petroleumfeedstocks. In embodiments, C/A blendstock comprises aromatic compoundsobtained by separation (e.g., via distillation or extraction) ofaromatic compounds selected from the group consisting of C9-C15single-ring aromatic compounds from petroleum feedstocks. Suitablepetroleum feedstocks comprise oil sand- and/or oil shale-derivedproducts that are inherently rich in cycloalkanes.

In an embodiment, C/A blendstock is produced by catalytic cyclizationand/or reforming of I/N blendstock prepared from triglyceride and/orfatty acid feedstocks as disclosed hereinabove. In this embodiment, I/Nblendstock may be produced via: (1) catalytic triglyceride dissociationinto fatty acids and glycerol, (2) glycerol removal, (3) oxygen removalfrom fatty acids (via catalytic decarboxylation and/or reduction) toyield normal paraffins, and, to the extent desired, (4) catalyticisomerization of a portion of these normal paraffins to yieldisoparaffins. In embodiments, I/N-C/A fuel comprises about 35 vol. % C/Ablendstock derived from catalytic processing of triglyceride feedstock.In embodiments, I/N-C/A fuel comprises about 65 vol. % I/N blendstockderived from catalytic processing of triglyceride feedstock and about 35vol. % C/A blendstock derived from catalytic processing of triglyceridefeedstock.

In another embodiment of the invention, C/A blendstock is produced frombiomass-derived lignin feedstock. C/A blendstock may be produced viacatalytic depolymerization of biomass-derived lignin feedstock followedby hydroprocessing as required to yield a desired proportion (forexample, JP-8-quality) of cycloalkanes and aromatics. In embodiments,the I/N-C/A fuel comprises about 20 vol. % C/A blendstock derived frompyrolysis of biomass-derived lignin. In alternative embodiments, I/N-C/Afuel comprises about 15 vol. % C/A blendstock derived from catalyticprocessing of lignin. In embodiments, I/N-C/A fuel comprises about 80vol. % I/N blendstock derived from Fischer-Tropsch processing of naturalgas, coal, and/or biomass, and about 20 vol. % C/A blendstock derivedfrom pyrolysis processing of biomass-derived lignin. In embodiments,I/N-C/A fuel comprises about 85 vol. % I/N blendstock derived fromcatalytic processing of triglyceride feedstock and about 15 vol. % C/Ablendstock derived from catalytic processing of lignin.

V. I/N-C/A Fuel

A finished I/N-C/A fuel may have “drop-in compatibility” with itspetroleum-derived counterpart, i.e. the I/N-C/A fuel may be blended inany proportion, from 0 vol. % to 100 vol. % with a petroleum-derivedcounterpart. The disclosed I/N-C/A fuel provides for the blending offuel components (including isoparaffins, normal paraffins, cycloalkanes,and/or aromatics), at least two of which are derived from disparateprocesses, to create UN-C/A fuel. In embodiments, at least 50 weightpercent of an aviation-grade UN-C/A kerosene fuel is derived from coal,natural gas, or a combination thereof. In embodiments, at least 50weight percent of an I/N-C/A fuel is derived from biomass. Inembodiments, at least 10 weight percent of an I/N-C/A fuel is derivedfrom non-cracked bio-oil. In embodiments, UN-C/A fuel has a cetanenumber of greater than about 70.

In embodiments, the I/N-C/A fuel complies with specifications for Jet Aand/or another civilian jet fuel. In embodiments, the I/N-C/A fuelcomplies with a military jet fuel specification selected from JP-8 andother military-grade jet fuel specifications.

In addition to meeting fuel property and performance requirements listedin U.S. military and ASTM (American Society for Testing and Materials)International aviation jet fuel specifications, in embodiments, anI/N-C/A-blended fuel will also meet applicable U.S. military-specifiedfit-for-purpose requirements that address a variety of fuel performanceand materials compatibility issues. As mentioned hereinabove,fit-for-purpose requirements refers to fuel property requirements thatare not necessarily addressed by military or ASTM standards, but areimportant to fuel performance and stability in jet engines and duringfuel handling, distribution, and storage. Examples of fit-for-purposerequirements include fuel compatibility with aircraft fuel and enginesystem materials of construction, adequate fuel performance incompression ignition (versus turbine) engines in a wide variety ofground environments, and possible fuel performance requirements relatedto swelling of elastomeric seals in, for example, turbine engines. Thesefit for purpose requirements, in addition to feedstock properties andASTM standards are used to determine the optimal ratio of the I/Nblendstock to the C/A blendstock.

VI. EXAMPLES Example 1 Fuel Sample A

A FT fuel produced from natural gas and containing iso-paraffinic andnormal paraffin hydrocarbons did not comply with density requirement ofthe JP-8 military specification (MIL-DTL-83133E). In this example, amixture of aromatic hydrocarbon fluid containing aromatic hydrocarbonsranging in carbon chain length from 8-16, was blended to a concentrationof 23% by weight with the FT fuel. A summary of results from Fuel SampleA compared to specification requirements outlined in MIL-DTL-83133E isprovided in Table 4.

TABLE 4 Results from Jet Fuel Specification Tests of Fuel Sample AComprising Blend of Aromatic Hydrocarbon and Fischer-Tropsch DerivedFuel Specification Test Sample A Military Spec Acid Number, mg KOH/gm0.003 0.015 max Aromatics, vol % 19.4 25 vol % max Olefins, vol % 0.0 5vol % max Sulfur, mass % 0.0 0.30 max Heat of Combustion, Btu/lb 1850018400 Distillation: 10% recovered, ° C. 172 205 max Endpoint, ° C. 274300 max Residue, vol % 1.4 1.5 max Loss, vol % 0.4 1.5 max Flash Point,° C. 48  >38 Freeze Point, ° C. −57 −47 max Hydrogen Content, mass %14.0 13.4 min API Gravity @ 60° F. 48.2 37.0-51.0 Specific Gravity @ 15°C., g/mL 0.787 0.775-0.84 

As seen in the data presented in Table 2, the resulting fuel had adensity of 0.788 g/mL achieving the minimum specification requirement of0.775 g/mL as defined by MIL-DTL-83133E while complying with all of theparameters contained within the specification. Data from gaschromatography of Sample A and a typical FT fuel is provided in FIG. 4.

Example 2 Fuel Sample B

The same FT fuel as used in Example 1 was blended at 82% wt. with 8% wt.of a mixed aromatic fluid and 10% wt. cycloparaffinic fluid. A summaryof Fuel Sample B results from key specification parameters is providedin Table 5.

TABLE 5 Results for Key Jet Fuel Specification Tests of Fuel Sample BComprising Blend of Aromatic and Cycloparaffin Hydrocarbons withFischer-Tropsch Derived Fuel Specific Freeze Flash HHV, Gravity, g/mLPoint,° C. Point, ° C. MJ/kg Mil Spec 0.775-0.84 −47 >38 C. >42.8Specification value is a lower heating value Sample B 0.779 −61.4 4846.1 Lab analysis FT Fuel 0.755 −56.7 48 46.6 Lab analysis

As seen in the results in Table 5, the resulting fuel Sample B possesseda MIL-DTL-83133 E specification compliant fuel with a density of 0.779g/mL.

Example 3 Fuel Sample C

Two hydrocarbon blendstocks, one consisting of normal- andiso-paraffinic hydrocarbon and the second consisting of a mixture ofaromatic and cycloparaffinic hydrocarbons, were produced exclusivelyfrom crop oil and blended to achieve a fuel sample complying with therequirements of MIL-DTL-83133E. In this example, neither fuel blendstockpossessed, on its own, the physical characteristics required by thespecification; however, through blending at a ratio of 44% normal andiso-paraffinic blendstock, and 66% aromatic and cycloparaffinicblendstock, the resulting fuel achieved the necessary characteristics. Asummary of results from Fuel Sample C compared to specificationparameters outlined in MIL-DTL-83133E is provided in Table 6. Data fromgas chromatography of Sample C and a typical JP-8 fuel is provided inFIG. 5.

TABLE 6 Results from Jet Fuel Specification Tests of Fuel Sample CComprising a Blend of Two Discrete Hydrocarbon Blendstocks Produced fromCrop Oil Specification Test Sample C Military Spec Aromatics, vol % 19.825 vol % max Olefins, vol % 1.9 5 vol % max Heat of Combustion, Btu/lb18400 18400 Distillation: 10% recovered, ° C. 171 205 max Endpoint, ° C.255 300 max Residue, vol % 1.2 1.5 max Loss, vol % 0.4 1.5 max FlashPoint, ° C. 49  >38 Freeze Point, ° C. −52 −47 max API Gravity @ 60° F.44.3 37.0-51.0 Specific Gravity @ 15° C., g/mL 0.805 0.775-0.84 

While preferred embodiments of the invention have been shown anddescribed, modifications thereof can be made by one skilled in the artwithout departing from the spirit and teachings of the disclosure. Theembodiments described herein are exemplary only, and are not intended tobe limiting. Many variations and modifications of the inventiondisclosed herein are possible and are within the scope of the invention.Where numerical ranges or limitations are expressly stated, such expressranges or limitations should be understood to include iterative rangesor limitations of like magnitude falling within the expressly statedranges or limitations (e.g., from about 1 to about 10 includes, 2, 3, 4,etc.; greater than 0.10 includes 0.11, 0.12, 0.13, etc.). Use of theterm “optionally” with respect to any element of a claim is intended tomean that the subject element is required, or alternatively, is notrequired. Both alternatives are intended to be within the scope of theclaim. Use of broader terms such as comprises, includes, having, etc.should be understood to provide support for narrower terms such asconsisting of, consisting essentially of, comprised substantially of,etc.

Accordingly, the scope of protection is not limited by the descriptionset out above but is only limited by the claims which follow, that scopeincluding all equivalents of the subject matter of the claims. Each andevery claim is incorporated into the specification as an embodiment ofthe present invention. Thus, the claims are a further description andare an addition to the preferred embodiments of the present invention.The discussion of a reference is not an admission that it is prior artto the present invention, especially any reference that may have apublication date after the priority date of this application. Thedisclosures of all patents, patent applications, and publications citedherein are hereby incorporated by reference, to the extent they provideexemplary, procedural or other details supplementary to those set forthherein.

1. Aviation-grade kerosene comprising: a first blendstock derived fromnon-petroleum feedstock and comprising primarily hydrocarbons selectedfrom the group consisting of isoparaffins and normal paraffins; and asecond blendstock comprising primarily hydrocarbons selected from thegroup consisting of cycloalkanes and aromatics.
 2. The aviation-gradekerosene of claim 1 wherein the second blendstock is derived fromfeedstock comprising non-petroleum feedstock.
 3. The aviation-gradekerosene of claim 1 that is capable of being blended withpetroleum-derived jet fuel in any proportion such that the resultingblend meets fuel grade specification of the petroleum-derived jet fuel.4. The aviation-grade kerosene of claim 3 comprising up to 95 volumepercent of first blendstock and up to 35 volume percent of secondblendstock.
 5. The aviation-grade kerosene of claim 4, comprising up to95 volume percent first blendstock, from about 0 volume percent to about30 volume percent cycloalkanes, and from about 0 volume percent to about15 volume percent aromatics.
 6. The aviation-grade kerosene as in claim5 wherein fit-for-purpose requirements are met.
 7. The aviation-gradekerosene of claim 6 wherein at least 50 weight percent of the keroseneis derived from coal, natural gas, or a combination thereof.
 8. Theaviation-grade kerosene of claim 6 wherein the second blendstock isderived from coal, biomass, oil-shale, tar, oil sands, or a combinationthereof.
 9. The aviation-grade kerosene of claim 6 wherein at least 50weight percent of the kerosene is derived from biomass.
 10. Theaviation-grade kerosene of claim 1 wherein at least 10 weight percent ofthe kerosene is derived from non-cracked bio-oil.
 11. The aviation-gradekerosene of claim 1 having a specific density in the range of from about0.775 g/mL to about 0.84 g/mL.
 12. The aviation-grade kerosene of claim11 having a freeze point below −47° C.
 13. The aviation-grade keroseneof claim 12 having a flash point of greater than 38° C.
 14. Theaviation-grade kerosene of claim 1 having a cetane number of greaterthan about
 70. 15. The aviation-grade kerosene of claim 1 wherein thenon-petroleum feedstock is selected from the group consisting of coal,natural gas, biomass, vegetable oils, biomass pyrolysis bio-oils,biologically-derived oils and combinations thereof.
 16. Theaviation-grade kerosene of claim 1 wherein the non-petroleum feedstockcomprises at least one component selected from the group consisting oftriglycerides and fatty acids.
 17. The aviation-grade kerosene of claim16 comprising from about 65 volume percent to about 95 volume percentfirst blendstock.
 18. The aviation-grade kerosene of claim 17 whereinthe second blendstock comprises pyrolysis products derived frompyrolysis of a second feedstock comprising at least one componentselected from the group consisting of high-cycloalkane content oilshales and oil sands.
 19. The aviation-grade kerosene of claim 17wherein the non-petroleum feedstock comprises at least one componentselected from the group consisting of triglycerides and fatty acids andwherein at least a portion of the second blendstock is produced bysubjecting a portion of the non-petroleum feedstock to cyclization,reforming, or both.
 20. The aviation-grade kerosene of claim 19 whereinthe kerosene comprises about 65 volume percent first blendstock andabout 35 volume percent second blendstock.
 21. The aviation-gradekerosene of claim 1 wherein the non-petroleum feedstock comprises atleast one component selected from the group consisting of natural gas,coal, and biomass and wherein the first blendstock comprises at leastone Fischer-Tropsch conversion product thereof.
 22. The aviation-gradekerosene of claim 1 wherein the second blendstock comprises at least oneproduct of pyrolysis of a feedstock selected from the group consistingof coal, oil shale, oil sands, tar, biomass and combinations thereof.23. The aviation-grade kerosene of claim 1 wherein the second blendstockcomprises at least one product of pyrolysis of biomass-derived lignin.24. The aviation-grade kerosene of claim 23 comprising from about 15volume percent to about 30 volume percent of the second blendstock. 25.The aviation-grade kerosene of claim 23 wherein the first blendstockcomprises at least one catalytic processing product of a componentselected from the group consisting of triglycerides and fatty acids. 26.The aviation-grade kerosene of claim 23 wherein the non-petroleumfeedstock comprises at least one component selected from the groupconsisting of natural gas, coal and biomass and wherein the firstblendstock comprises at least one Fischer-Tropsch conversion productthereof.
 27. The aviation-grade kerosene of claim 1 comprising about 95volume percent of the first blendstock and about 5 volume percent of thesecond blendstock, wherein the second blendstock comprises primarilyhigh density, low freeze point aromatics.
 28. The aviation-gradekerosene of claim 1 comprising at least 50 weight percent ofhydrocarbons selected from cycloalkanes and aromatics, said hydrocarbonsderived from coal, biomass, or a combination thereof.